(1) Field of the Invention
This invention relates to an action for an upright piano, the action being the mechanism which transmits to the piano strings the impetus given by the player's touch.
An ideal piano action would have the following characteristics: Firstly, the piano player should have good control over the hammer blow, in order to be able to vary the character of the notes played. Secondly, there must be escapement so that the hammer can rebound freely after striking the string, even if the key is still being depressed by the player. Thirdly, the motion of the hammer should be checked after it has rebounded from the string. Fourthly, the player should be able to repeat the note immediately and continuously if desired, even if the key is not fully released. Fifthly, the damping action should be instantaneous and silent.
Different piano actions approach these ideals to varying degrees. The action of a grand piano is generally considered to much more closely approach these ideals than the action of an upright piano. For example, the grand piano action allows for immediate and continued repetition of a note, even if the key has not fully returned to its normal (undepressed) position, while the upright action requires that the key return to or almost to its normal position before the note can be repeated. This difference is due to the superior design of the grand piano whippen assembly.
The conventional upright piano action has a single simple escapement, that of the hammer from the jack of the whippen assembly. The head of the jack is ordinarily in contact with the butt of the hammer. When the key is depressed the jack is moved upwardly, forcing the butt of the hammer to rotate upwardly about the pivot point on its flange. At a certain point before the hammer contacts the string, escapement takes place. The jack rotates out from under the butt of the hammer, freeing the hammer to continue under its own inertia towards the string and to rebound freely after impact. After rebounding from the string, the catcher is caught by the backcheck and held in this position as long as the key is depressed. In order for the note to be repeated, the key must be fully released or very nearly so, so that the jack can drop back into position under the hammer butt.
By contrast, in the grand piano action the jack can drop back under the knuckle before the key is fully released. In a grand piano action, there is a compound escapement, involving the jack coming into contact with a regulating button and being forced to rotate out from under the knuckle of the hammer, and also the repetition lever coming into contact with a drop screw. As the key is depressed, the escapement takes place and the hammer flies freely towards the string under its own inertia. After rebounding from the string, the catcher is caught by the backcheck and held in this position as long as the key is depressed. Then, when the key is released slightly, the repetition lever supports the knuckle, allowing the jack to drop back into position. Consequently, if the key is depressed again, the jack can immediately move upwards and attack the knuckle. Repeating a note immediately and continuously is thus far easier than on an upright piano.
Checking in a grand piano action must generally be more secure than in an upright action, due to the force in the direction of the string exerted by the repetition lever on the knuckle on the hammer shank.
With respect to damping in a grand piano, the damper is held onto the string by gravity. As soon as the key is released, the damper starts to drop back onto the string. The damper is also under the direct control of the key. When the key is depressed the effect produced by gravity on the damper must be overcome. The fact that the damper is under direct control of the key and that the damper is held on the string only by gravity gives the grand piano a precise touch which is appreciated by many players.
By contrast, the damper in the upright piano is held onto the string by means of a small damper spring. When the key is depressed the force exerted by the spring on the damper must be overcome. Overcoming this force is a gradual process and the touch of the upright piano keys is consequently somewhat different from that of the grand piano. The spring may also deteriorate with time and thereby produce an inconsistent touch. If sufficient deterioration occurs, the damper may be left in imperfect contact with the string, thereby reducing its ability to dampen string vibration. Also, the damper is not under the direct control of the key but rather is activated via an intermediate lever. These factors result in a damper action which has a less controlled and consistent touch and which is more prone to mechanical problems than the damper action in a grand piano.
In addition to superior note repetition, the grand piano action has an advantage over the upright piano action in relation to the operation of the left or soft pedal, largely due to the fact that the hammer and damper actions are structurally independent of each other.
In the grand piano, when the left pedal is depressed, the key frame slides laterally on the key bed. The hammer action is attached to the key frame, and consequently it also slides laterally when the soft pedal is deprssed. If a key in the treble section is played, the hammer ordinarily strikes three strings. However, if the key is played while the soft pedal is being depressed, the hammer will move laterally with the key frame and strike only two strings. A softer sound will consequently be produced.
In a conventional upright piano, movement of the key frame is generally not possible, because the dampers are attached to the main action rail, as are the hammer flanges. An exception is shown in U.S. Pat. No. 608,177 (Cobb), but the structure in that case is impractical for a variety of reasons, and the damping arrangement is different from in the present invention.
Since the dampers must not move in relation to the strings (because they must be seated properly on the strings in order to dampen string vibration), this means that the hammer action, being supported on the same main action rail, cannot move with respect to the strings. By contrast, in the grand piano, the dampers are attached to a damper flange rail which is independent from the main action rail. The key frame can therefore be made free to move laterally when the soft pedal is used, without having the dampers shift.
In a conventional upright piano, softening is achieved by having the hammer rail move the hammers closer to the strings when the soft pedal is depressed. If a key is played with the soft pedal depressed, some of the motion normally imparted to the hammer is lost because of the shorter distance between the hammers and the strings and because of the shorter period of contact between the jack and the hammer butt resulting from the shifting of the hammer rail, so the hammer strikes the strings with less force than normal. A hammer in the treble section of the piano will normally strike three strings, but will strike them with less force than usual when the soft pedal is used, and will therefore produce a softer sound.
(2) Description of the Prior Art
U.S. Pat. No. 608,177 (Cobb), mentioned above, shows lateral shifting of the keyboard and action in response to the soft pedal, but is impractical in its actual structure. The hammer rail and the key frame shift laterally, but via separate actuation rather than being connected together as a unit.
U.S. Pat. Nos. 332,328 (Hofmann) and 473,944 (Merkel), show hammer actions similar to the one of the present invention, but their damping mechanisms renders them impractical because of space limitations. Also, there is no independence of the hammer action and the damping action in either patent.
United Kingdom Pat. No. 4364/1901 (Midgley), shows a gravity-biased vertical-motion damping mechanism actuated by the back of each key, but it is structurally different from the damping mechanism in the present invention, and the dampers are located above instead of below the hammers.
U.S. Pat. No. 481,121 (Richardson et al), shows a vertically-oriented damper lifter, but for a pianoforte with horizontal rather than upright strings.
U.S. Pat. Nos. 135,820 (Kuhner) and No. 904,177 (Cross), show dampers actuated by the back of the key, without direct linkage, but are otherwise irrelevant.